Method and Apparatus for a plug with a shear landing feature for untethered object

ABSTRACT

A plug assembly includes a shear landing feature, offering temporarily one or more seating surfaces for an untethered object. The shear landing feature can shear within a set plug if the force induced by a fluid pressure uphole of a landed untethered object exceeds the shear rating of the shear landing feature. A secondary fixed seating surface offers a landing and seating surface for a secondary untethered object, used typically for back-up operations.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a Continuation-In-Part (CIP) application of U.S Application Serial No. 17/275,509 filed on March 11th, 2021, titled “Methods and Apparatus for providing a plug with a two-step expansion” naming Gregoire M Jacob as inventor and a Continuation-In-Part (CIP) application of U.S. Application Serial No. 18/101,091 filed on Jan. 24th, 2023, titled “Method and Apparatus for a plug with a retractable pivoting mechanism for untethered object” naming Gregoire M Jacob as inventor. All the foregoing applications are hereby incorporated herein by reference in their entirety.

BACKGROUND

This disclosure relates generally to methods and apparatus for providing a plug inside a tubing string containing well fluid. This disclosure relates more particularly to methods and apparatus for providing a plug including a shear landing feature, offering temporarily or permanently one or more seating surfaces for untethered objects.

FIG. 1 refers to one environment example in which the methods and apparatus for providing a plug inside a tubing string containing well fluid, described herein, may be implemented and used.

FIG. 1 illustrates a typical cross section of an underground section dedicated to a cased-hole operation. The type of operation is often designated as Multi-Stage-Stimulation, as similar operations are repeatedly performed inside a tubing string in order to stimulate the wellbore area.

The wellbore may have a cased section, represented with tubing string 1. The tubing string contains typically several sections from the surface 3 until the well end. The tubing string represented schematically includes a vertical and horizontal section. The entire tubing string contains a well fluid 2, which can be pumped from surface, such as water, gel, brine, acid, and which can also come from the downhole reservoir or downhole formation such as produced fluids or condensates, like water and hydrocarbons in liquid or gas form.

The tubing string 1 can be partially or fully cemented, referred as cemented stimulation, or partially or fully free within the borehole, referred as open-hole stimulation. Typically, a stimulation will include temporary or permanent section isolation between the formation and the internal volume of the tubing string.

The bottom section of FIG. 1 illustrates several stimulation stages starting from well end. In this particular well embodiment, at least stages 4 a, 4 b, 4 c have been stimulated and isolated from each other. The stimulation is represented with fluid penetration inside the formation through fracturing channels 7, which are initiated from a fluid entry point inside the tubing string. This fluid entry point can typically be provided by perforations or sliding sleeves openings, within the tubing string 1.

Each isolation includes a set plug 6 with its untethered object 5, represented as a spherical ball as one example.

The stimulation and isolation are typically sequential from the well end. At the end of stage 4 c, after its stimulation 7, another isolation and stimulation, represented as subsequent stage 4 d, may be performed in the tubing string 1.

In this representation, a toolstring 10 is conveyed via a cable or wireline 9, which is controlled by a surface unit 8. Other conveyance methods may include tubing conveyed toolstring or coiled tubing. Along with a cable 9, a combination of gravity, tractoring and fluid pump-down may be used to bring the toolstring 10 to the desired position inside the tubing string 1. The toolstring 10 may convey an unset plug 11, dedicated to isolating stage 4 c from stage 4 d.

Additional pumping rate and pressure may create a fluid stimulation 7 inside the formation located on or near stage 4 d. When the stimulation is completed, another plug may be set and the overall sequence of stages 4 a to 4 d may start again. Typically, the number of stages within a wellbore may be between 10 and 100, depending on the technique used, the length of the well and spacing of each stage.

By convention, the downhole direction 13 is directed from top to bottom. If observing a tubing string 1, the downhole direction 13 would be the direction from surface towards the well end. The uphole direction 14 is directed from bottom to top, opposite to the downhole direction. If observing a tubing string 1, the uphole direction 14 would be the direction from the well end towards surface. Therefore, downhole pumping would correspond to pumping well fluid 2 towards the downhole direction 13. Uphole pumping or flowing, typically referred as flowback, would correspond to pumping or flowing well fluid 2 towards the uphole direction 14.

There is a continuing need in the art for methods and apparatus for methods and apparatus for providing a plug inside a tubing string containing well fluid. Preferably, the plug is provided using a 2-step expansion, first expanding a first group of deformable plug components, second expanding a second group of more rigid plug components. Preferably, the plug is provided with a temporarily seating surface for an untethered object.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more detailed description of the embodiments of the disclosure, reference will now be made to the accompanying drawings.

FIG. 1 is a wellbore cross-section view of typical Multi-Stage-Stimulation operation ongoing, with three stages completed and a toolstring conveyance to install the third isolation device for a fourth stage.

FIG. 2 is a cross-section view of an embodiment of a plug assembly, in a run-in hole position inside a tubing string, over a setting tool having a caged untethered object or ball-in-place.

FIG. 3 is a cross-section view of a ball-drop plug, activated by a cup. The plug is depicted in set position inside a tubing string.

FIG. 4 is two cross-section of a retractable pivoting mechanism, including a latching feature, with four segments in their closed position with a first-size untethered object, and in opened position with a second-size untethered object.

FIG. 5 is two isometric cross-section views of a set plug, including an integral locking ring, and retractable pivoting mechanism including a latching feature, as depicted in FIG. 4 .

FIG. 6 is a cross-section view of a plug including a shear landing feature. The plug is represented in an unset position within a tubing string.

FIG. 7 is a cross-section view of the plug of FIG. 6 , after being set within the tubing string.

FIG. 8 is cross-section view of the set plug of FIG. 7 , after the landing of an untethered object on the shear landing feature.

FIG. 9 is a cross-section view of the set plug of FIG. 8 , after the shearing of the shear landing feature and flowing down of the untethered object.

FIG. 10 is a cross-section view of the set plug of FIG. 9 , after the landing of a second-size untethered object on a fixed seating surface of the set plug.

FIG. 11 is an isometric cross-section view of the set plug of FIG. 7 .

FIG. 12 is an isometric cross-section view of the set plug of FIG. 8 , with a first-size untethered object landed on the shear landing feature.

FIG. 13 is an isometric cross-section view of the set plug of FIG. 10 , with a second-size untethered object landed on a fixed seating surface of the set plug.

FIG. 14 is an isometric view of three parts, securing ring, shear landing ring and integral locking ring.

FIG. 15 is a flow diagram representing a technique sequence of using a plug with a shear landing feature.

DETAILED DESCRIPTION

It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention.

A reference to U.S. Application Serial No. 17/275,509 filed Mar. 11, 2021, titled “Methods and Apparatus for providing a plug with a two-step expansion” can provide a detailed description of the FIGS. 1 to 2 . A reference to U.S. Application Serial No. 18/101,091 filed Jan. 24, 2023, titled “Method and Apparatus for a plug with a retractable pivoting mechanism for untethered object” can provide a detailed description of the FIGS. 3 to 5 . A quick background reference is done in this US application, as several embodiments are the same compared to the new U.S. Application as CIP with the improvement further described in FIGS. 6 to 15 .

FIG. 2 represents a cross-section view of an unset plug or run-in-hole plug, inside the tubing string 1, along a tool axis 12. FIG. 2 represents the unactuated or undeformed position for the plug and a retrievable setting tool, which allows traveling inside the tubing string 1.

The plug may include the following components:

-   an expandable continuous seal ring 170, -   an expandable gripping ring 161, which preferably includes anchoring     devices 74, -   a back-pushing ring 160, including shear devices 65 which may be     positioned on the inner diameter of the back-pushing ring 160, -   a locking ring 410, which includes a conical external shape matching     the inner surface of the expandable gripping ring 161 and the inner     surface of the expandable continuous seal ring 170. The locking ring     410 may include a hemispherical inner surface 419 and a conical     inner surface 416, and, -   a hemispherical cup 411.

The retrievable setting tool may include the following components:

-   an external mandrel 414, which may include a cylindrical pocket 418.     The pocket 418 may have a channel 415 linking the pocket 418 with     the well fluid 2 present inside the tubing string 1. In this     representation, the external mandrel 414 may contact the locking     ring 410 along the conical surface 416. In addition, the external     mandrel 414 may contact the hemispherical cup 411 along a conical     surface 417, -   a rod 412 which can move longitudinally relative to the external     mandrel 414. The rod 412 may provide a link to the shear devices 65,     securing the longitudinal position of the back-pushing ring 160.

In addition, an untethered object 413 may be included inside the pocket 418 of the external mandrel 414.

This embodiment may be referred to as ‘ball in place’, where the untethered object 413 may be a ball which is included in the retrievable setting tool. Other embodiments for the untethered object 413 may be a pill, a dart, a plunger, preferably with at least a hemispherical or a conical shape.

Further the plug may be set within the tubing string 1, after the relative longitudinal movement of the rod 412 relative to the external mandrel 414.

The plug with the above listed components may typically be conveyed on a toolstring 10, including a setting tool and a setting adapter. The setting adapter, also known as adapter kit, may include the external mandrel 414 and the internal rod 412. The external mandrel 414 and the internal rod 412 may be specific to adapt to the type of conveyed plug. The toolstring 10, as depicted in the background FIG. 1 may be conveyed via a wireline cable 9, or via a coiled-tubing or flexible tubing, or via a tractoring device, or pumped down independently from surface inside the well fluid 2. The toolstring 10 may include other measuring or actuating components, such as positioning or formation measurement devices, like CCL for Casing Collar Locator, GR for Gamma Ray, or any environment measurement such as pressure, temperature, resistivity, sonic, ultrasonic and any combination of the above. Typically, the toolstring 10 may also include perforating guns to create perforating channels, leading to fracturing channels 7, as depicted in FIG. 1 . The toolstring 10 may also include a setting tool, such as an actuation tool which provides an actuation force, typically a longitudinal force, along axis 12, with the purpose to displace longitudinally the external mandrel 414 relative to the internal rod 412, or reversed. The setting tool may provide its longitudinal actuation force through different means, such as power charge, hydrostatic downhole pressure, electric motor, turbine, embedded explosive or any combination. The setting tool may be suited to actuate or set the plug, such as the one depicted in FIG. 2 , by longitudinally displacing the external mandrel 414 relative to the internal rod 412, after receiving a command to start the relative displacement. The command to start the relative displacement may come from a wired signal to an addressable switch, from an internally programmed signal inside the toolstring 10, based on a position or an RFID tag or specific environmental conditions within the tubing string 1, or from a wireless signal sent by another device within the tubing string 1, or within a nearby tubing string or within a surface device communicating with the toolstring 10.

FIG. 3 represents a variation of the plug depicted in FIG. 2 , whereby a hemispherical cup 110 includes a larger inner diameter compared to the cup 411 of FIG. 2 . The hemispherical cup 110 may allow to seat a larger untethered object 5. The plug of FIG. 3 would be more suited for ball-drop operation, whereby the untethered object 5 is released from surface, rather than from inside the toolstring 10.

FIGS. 4 and 5 depict a plug with a retractable pivoting mechanism, including a latching feature.

FIG. 4 represents two cross-section views 401 and 402 of an embodiment including four segments 380 a, 380 b, 380 c and 380 d, further referred as 380 a-d, connecting each to a hemispherical cup 381. The connection between each of the depicted segments 380 a-d and the hemispherical cup 381 may occur thanks to a pivoting axis 321, which may include the feature of torsion spring 322.

In view 401 of FIG. 4 , the four retractable pivoting segments 380 a-d are depicted in their closed position with the seating of an untethered object 19. In the closed position, each segment of 380 a-d may pivot around the rotation axis 321 so that each segment is contacting radially each other’s to form a continuous seating ring and form a continuous seating surface 383 on its uphole edge, including a through cylindrical surface 382. In the closed position, each segment 380 a-d may also contact the flared or conical surface 390 of each segment with a corresponding flared or conical surface 391 of the hemispherical cup 381.

The seating surface 383 may be adapted, such as a chamfer or flared surface to the reception of an untethered object 19. The diameter of the trough cylindrical surface 382 may be smaller than the external diameter of the untethered object 19. Further, the diameter of a cylindrical section 384 of the hemispherical cup 381 may be larger than the external diameter of the untethered object 19.

In view 402 of FIG. 4 , the four segments 380 a-d are depicted in their opened position. In the opened position, the pass-through area of the four segments 380 a-d, may not be continuous, though may have a minimum cylindrical pass-through dimension which allows the untethered object 19 to pass without being blocked. Overall, the untethered object 19 may be able to pass through the embodiment 402 of FIG. 4 , towards both directions uphole and downhole. In case the four segments 380 a-d are in their closed position, the untethered object 19 would be blocked and seated if traveling towards downhole. If traveling towards uphole, with a sufficient force coming typically from a well fluid flow, the untethered object 19 would be able to overcome the torque of the torsion spring 322 and pass through the embodiment shown in view 401 by a combined action of flow force and contact pushing the four segments 380 a-d on their below surface 392.

The uphole edge 385 of the cylindrical section 384 may provide a seat for another size untethered object 20. The untethered object 20 would have a diameter larger than the untethered object 19, depicted in view 401. In their opened position, the four segments 380 a-d may have a minimum cylindrical pass-through dimension represented at dimension 386. The minimum cylindrical pass-through dimension would allow to pass the untethered object 20, which diameter is smaller than the dimension 386. The diameter of the untethered object 20 may be large enough to be stopped and seat on the edge 385 of the cylindrical section 384.

The landing of the untethered object 19 on the closed segments 380 a-d, as would be seen on view 401 of FIG. 4 , may be facilitated by a pumping down action of well fluid 2 from surface. The landing of the untethered object 19 on the closed segments 380 a-d up may be observed as a pressure increase, typically measured at surface, representing a sudden restriction of the downhole flow, also referred as ball landing signature. Subsequent to ball landing, further operation like perforating of the tubing string 1 may be performed. In case for example of a misfire, corresponding to the inability to perforate and therefore the inability to create flow channels 13 as depicted in FIG. 1 , the volume of the tubing string 1 may be constraint, with the impossibility to further pump downhole.

FIG. 5 represents different views of cross-sectional plugs which includes an integral locking ring 399. The integral locking ring 399 may replace the combination of the locking ring 111 or 410 and the hemispherical cup 411, 110 or 381, without modifying the function or operation of the seatings of untethered objects.

View 377 of FIG. 5 represents a plug set inside the tubing string 1. The plug includes an integral locking ring 399. The depicted plug may include the segments 380 a-d, in their closed position, with the addition of a landed untethered object 19 as described in view 401 of FIG. 4 . Additional items included in the depicted plug may be the expandable gripping ring 161, the expandable continuous sealing ring 170 and the back-pushing ring 160.

View 378 of FIG. 5 represents the same plug as in view 377 of FIG. 5 , with the replacement of the untethered object 19 with the untethered object 20, and having the segments 380 a-d in their opened position. The untethered object 20 may have landed on the continuous seating surface 397 which is similar to surface 385 described in view 402 of FIG. 31 .

Both embodiments depicted in FIGS. 4-5 show the possibility for a plug to include multiple landing and seating surface for untethered objects. Multiple seating surfaces offer the possibility to include operations with subsequent isolations using different sizes untethered object. The typical use for depicted embodiment would include contingency operations in case of malfunction of sections inside the toolstring. For example, in case of multi-stage-stimulation, a malfunction could be a misfire for the perforation, impairing further pump down of well fluid 2 inside the tubing string. Having a possibility to replace or exchange the seated untethered object for a limited and dedicated time would allow to have a temporary flow exit at the position of the last set plug.

The proposed invention, depicted in FIGS. 6-13 propose an alternative of prior disclosures. The temporary seating surface for an untethered object would be materialized with a shear landing feature.

FIGS. 6-13 depict an embodiment for a plug with a shear landing feature.

FIG. 6 represents a cross-section view of a plug, in an unset or conveying position, within a tubing string 1 filled with well fluid 2. The plug may comprise the following components:

-   an expandable continuous sealing ring 170 -   an expandable gripping ring 161, which may include one or more     anchoring devices, represented as buttons 74 -   an integral locking ring 180 -   a back-pushing ring 160 -   a shear landing ring 190, secured within the integral locking ring     180 with a securing ring 195.

The descriptions made in U.S. Application 17/275,509 filed Mar. 11, 2021 for the continuous expandable seal ring 170, the expandable gripping ring 161, the anchoring devices 74, the back-pushing ring 160, can be taken as reference for this current CIP application.

All the plug components, 170, 161, 74, 160, 180, 190, 195, including the untethered objects 21 and 22, may be built out of dissolvable material. The dissolvable material may be a metallic alloy, a plastic alloy or a composite material which may dissolve or decompose within the well fluid 2 over time. The dissolving or decomposition may include an oxidation-reduction or corrosion reaction with some components of the well fluid 2. Some environmental conditions may influence the dissolving of some of the plug dissolving components, such as the well fluid 2 temperature, pressure, salinity, pH, density, movement, gas/fluid/solid content proportions, and chemical composition. The plug components may include different types of dissolving materials, which may have different dissolving rate and different mechanical properties, such as yield strength, ductility, hardness, based on the function within the plug. Coatings and heat treatment may also influence dissolving rate and mechanical properties of the different type of dissolving materials. Within the same part, multiple materials with different properties, such as mechanical or dissolving, may be used.

The shear landing ring 190 may be a continuous ring allowing a continuous contact with the untethered object 21, potentially providing a fluid or pressure isolation when the two parts 190 and 21 are in contact with each other’s. The shear landing ring 190 may be built using a material having an expected shear behavior when solicitated in shear, and particularly when solicitated in circumferential shear, as further depicted in FIG. 9 .

FIG. 7 represents a cross-section view of the plug of FIG. 6 in a set position. To achieve a set position, the back-pushing ring 160 may have moved longitudinally relative to the integral locking ring 180, typically thanks to the force provided by the setting tool within the toolstring 10. The longitudinal movement of the back-pushing ring 160 may have induced a longitudinal movement of the expandable gripping ring 161 and the expandable continuous sealing ring 170. The longitudinal movement of the items 161 and 170 over the flared outer surface of the integral locking ring 180 may in turn induce a radial expansion of the same items 161 and 170. The radial expansion of both items 161 and 170 may be stopped when the anchoring devices 74 of the expandable gripping ring 161 are contacting the internal surface of the tubing string 1.

During the setting process of the plug as depicted in FIG. 7 , the shear landing feature 190 may have not moved relative to the integral locking ring 180, and may have not been solicitated.

FIG. 8 represents a cross-section view of the set plug of FIG. 7 . In FIG. 8 , an untethered object 21 has landed on the shear landing ring 190.

The untethered object 21 may be carried within the toolstring 10. The untethered object 21 may also be launched from surface and pumped down with well fluid 2. The storage position and launching point of the untethered object 21 may depend on the operation type or on the size, shape or diameter of the untethered object 21.

Also note that the untethered object 21, represented as a ball or sphere, may have the shape of a pill, a dart, a cone, or any external shape matching the shear landing ring 190. The untethered object 21 may also include some internal gas-filled, typically air, cavity, or include an association of different materials. The untethered object 21 may also include some measuring and recording capability.

Typical operation to land the untethered object 21 on the shear landing ring 190 may include downhole pumping of well fluid 2, towards the downhole direction. The flow of well fluid 2 is represented with arrows 44. After the landing of the untethered object 21 on the shear landing ring 190, the well fluid 2 may be pressurized from surface, typically through pumping activity, which may induce a pressure differential across the set plug, whereby the set plug creates a flow restriction.

Typical pressure differential uphole compared to downhole of the set plug, as on FIG. 8 , may reach a range of 1,000 to 20,000 psi [6.9 MPa to 138 MPa]. The set plug may block or divert a portion of the fluid flow 44 and build an over-pressure uphole of the set plug. The rule governing fluid flow and fluid pressure within a tubing string is typically referred as Bernoulli equation, and in case of high flow rates across a limited flow-through area represented as potential gaps remaining between the set plug and the tubing string 1, the pressure build-up is typically referred as Venturi effect. The local created fluid over-pressure P may induce a force F on all exposed surface S, following the formula F = P / S.

As depicted in FIG. 8 , a regular pressurizing or fracturing operation may be performed, uphole of the set plug, using the landed untethered object 21, and keeping the uphole pressure below a predetermined rating of the shear landing ring 190. As an illustration example, the rating of shear landing ring 190 may correspond to a fluid pressure of 12,000 psi, uphole of the set plug with untethered object 21. It means, as long as the uphole pressure of well fluid 2 is kept below the rating of the shear landing ring 190, the shear landing ring 190 may keep its geometrical shape and function. For example, the pressure of well fluid 2 may be kept around 10,000 psi for the pressurizing or fracturing operation. If no failure of operation steps has been observed, a sequential plug, similar to the plug set in FIG. 7 , may to be set uphole of the last set plug inside the tubing string 1, and further operations may continue. If, in another scenario, there is a failure to perforate above the set plug with untethered object 21, then there is no exit of well fluid 2 inside the tubing string 1, and an intervention may be needed. In prior art solution, typically, a mill-out intervention would be necessary to mill the set plug and provide a new fluid exit from the previous opening inside the tubing string 1, downhole of the last set plug.

With the proposed invention, a dedicated and focused pumping pressure could be applied uphole of the set plug with the untethered object 21. For example, a pressure around or just above the rating of the shear landing ring could be applied, like 12,050 psi, to keep the same illustration example. With a pressure above the rating of the shear landing ring 190, the shear landing ring 190 may shear at a shear circumference and be separated in two or more parts.

FIG. 9 represents a cross-section view of the set plug of FIG. 8 , whereby the shear landing ring 190 has sheared due to a load, uphole applied on the untethered object 21, which exceeds the shear rating of the shear landing ring 190. As depicted, the shear landing ring 190 may be separated in two sections, one fixed section 191, staying between the integral locking ring 180 and the securing ring 195, and a sheared section 192, released with the untethered object 21 inside the well fluid 2, downhole of the set plug. The shear circumference may be depicted as a virtual dash line cylinder 45. The movement of the untethered object 21 and the shear section 192, after the shear event of the shear landing ring 190, may be symbolized with arrow 46.

After the shear of the shear landing ring 190, the set plug may still be functional and suited to receive another untethered object, larger than the untethered object 21, on its fixed seating surface 196.

FIG. 10 represents a cross-section view of the set plug of FIG. 9 , after the shear of the shear landing ring 190, and after the landing of another untethered object 22 on the fixed seating surface 196. After the shear of the shear landing ring 190, another operation may have been performed like providing perforations inside the tubing string 1 uphole of the set plug. A new pump down of well fluid 2 may be possible with the ability to pump down another untethered object, depicted as item 22. The pumping of well fluid 2 may be symbolized with arrows 47. The pumping 47 of well fluid 2 may be similar to the pumping 44 depicted in FIG. 8 . The pumping 47 may carry the untethered object 22, typically including a larger external dimension as untethered object 21. The untethered object 22 may be suited to land and seat on the fixed seating surface 196. The fixed seating surface is represented as a continuous flared surface, typically a chamfer, on the internal diameter of the securing ring 195. The contact of the fixed seating surface 196 with the untethered object 22 may provide a fluid or pressure isolation. In other embodiment not depicted, the fixed seating surface 196 may be located directly on the integral locking ring 180.

With the untethered object 22 landed on the fixed seating surface 196, another downhole operation could be performed, like pressurizing or fracturing operation uphole of the set plug.

FIG. 11 is an isometric cross-section view of the set plug, similar to the plug depicted in FIG. 7 . Similar items are depicted compared to FIG. 7 . In particular, a more focused view on the shear landing ring 190, the securing ring 195 inside the integral locking ring 180, may be depicted. The securing ring 195 may be assembled to secure the shear landing ring 190 within the internal diameter of the integral locking ring 180. Possible assembly for the securing ring 195 within the integral locking ring 180 may include screwing, pining, gluing, press-fitting, welding. Additional fixing parts such as screws, snap-rings may be added to secure the parts assembly.

FIG. 12 is an isometric cross-section view of the set plug, similar to the plug depicted in FIG. 8 , with the untethered object 21 landed and seated on the shear landing ring 190.

FIG. 13 is an isometric cross-section view of the set plug, similar to the plug depicted in FIG. 10 , with the untethered object 22 landed and seated on the fixed landing surface 196.

FIG. 14 is an isometric view of three parts of the plug assembly, namely the securing ring 195, the shear landing ring 190 and the integral locking ring 180, seen in an exploded allignement.

FIG. 15 represents a technique sequence 520, which includes the major steps of a possible operation sequence depicted in FIGS. 6-10 .

Step 521 corresponds to the deployment of a plug assembly, as depicted in FIG. 6 , over a toolstring 10, inside a tubing string 1 containing well fluid 2. The plug assembly includes a shear landing feature, represented as a shear landing ring 190 in FIGS. 6-10 .

Step 522 corresponds to the setting of the plug assembly, using the action of the toolstring 10, inside the tubing string 1, as depicted in FIG. 7 .

Step 523 corresponds to the release of first-size untethered object 21, suited to land and seat on the shear landing ring 190.

Step 524 corresponds to the landing of the untethered object 21 on the shear landing ring 190, as depicted in FIG. 8 .

Step 525 corresponds to the potential trial of a downhole operation. Typically, it could correspond to perforating operation or sleeve opening uphole of the set plug with the seated untethered object 21.

Step 526 corresponds to a sequential operation after step 525 in case of the success of the step 525. For example, the perforating operation or sleeve opening happened as planed and subsequent operation step can be performed, like for example the pressure pumping or fracturing of the zone above the last set plug in step 522-524, while keeping the pressure of the well fluid 2 within the rating limit of the shear landing ring 190.

Step 527 corresponds to a sequential operation after step 525 in case of the failure of step 525. For example, the perforating operation may have occurred a misfire or the sleeve shifting may be stuck closed. In case of step 527, the volume of well fluid 2 above the set plug with untethered object 21, as set in step 522-524, may be constrained with no possible fluid exit downhole.

Step 528 corresponds to the pressurizing of well fluid 2 inside the tubing string 1, uphole of the set plug with untethered object 21. The pressure of the well fluid 2 would corresponds to an equivalent force on the untethered obj ect 21 which would exceed the shear rating of the shear landing ring 190.

Step 529, sequential of step 528, corresponds to reaching a pressure exceeding the shear rating of the shear landing ring 190, having for consequence to shear the shear landing ring 190 into two or more sections, at least a fixed section 191 and a sheared section 192, as depicted in FIG. 9 . As a secondary consequence, the sheared section 192 of the shear landing ring 190 and the untethered object 21 would flow together passed the inside of the set plug and flow downhole of the set plug within the tubing string 1 with the well fluid 2.

Between step 529 and step 530, an additional downhole operation may be performed, such as conveying downhole a new toolstring with perforating guns or a new toolstring to operate shifting sleeves. Typically, after the re-opening of the tubing string 1 as described in step 529, a new potential pump-down operation would be used to correct the failure which would have occurred in step 527.

Step 530 corresponds to the release of a second-size untethered object 22. Typically, the second-size untethered object 22 would be larger in outer dimensions compared to the first-size untethered object 21, and the second-size untethered object 22 would be suited to land and seat on the fixed seating surface 196 within the set plug. Typically, at this point of the described operation, the second-size untethered object 22 would be launched from surface, and could be considered as a back-up untethered object.

Step 531 corresponds to the landing of the second-size untethered object 22 on the fixed seating surface 196.

Step 532 corresponds to the performance of a downhole operation, typically the pressure pumping or fracturing of the zone above the last set plug in step 522-524. 

What is claimed is:
 1. A method comprising: deploying a plug assembly including a shear landing feature, into a tubing string containing well fluid, whereby the shear landing feature includes a seating surface suited to receive a first-size untethered object, whereby the shear landing feature includes a shear rating, whereby the plug assembly includes a fixed seating surface suited to receive a second-size untethered object, whereby the first-size untethered object is able to pass through the plug assembly including the fixed seating surface; setting the plug assembly into the tubing string; releasing a first-size untethered object inside the well fluid of the tubing string; contacting the seating surface of the shear landing feature with the released first-size untethered object; pressurizing the well fluid inside the tubing string, uphole of the set plug assembly with the contacted first-size untethered object, whereby the pressure of the well fluid induces a force on the first-size untethered object, wherein the force localized on the shear landing feature exceeds the shear rating of the shear landing feature; shear the shear landing feature and flow down the first-size untethered object; releasing a second-size untethered object inside the well fluid of the tubing string, suited to land on the fixed seating surface of the plug assembly; contacting the fixed seating surface of the plug assembly with the released second-size untethered object.
 2. The method of claim 1, further dissolving at least one component of the plug assembly or the untethered objects.
 3. The method of claim 1, further comprising: performing a downhole operation, after contacting the first-size untethered object on the seating surface of the shear landing feature, or after contacting the second-size untethered object on the fixed seating surface of the plug assembly, whereby the downhole operation includes perforating, sleeve shifting, measurements and recording, or pressure pumping.
 4. The method of claim 1, whereby the shear rating of the shear landing feature does not exceed an overall differential pressure rating of the set plug assembly inside the tubing string.
 5. The method of claim 4, whereby the shear rating of the shear landing feature corresponds to a range of 70% to 100% of the overall differential pressure rating of the set plug assembly inside the tubing string.
 6. The method of claim 1, whereby the plug assembly includes: an expandable continuous sealing ring, an expandable gripping ring, an integral locking ring, wherein the expandable continuous sealing ring and the expandable gripping ring include a flared inner surface, wherein the expandable continuous sealing ring and the expandable gripping ring are coupled together longitudinally through a conical or an annular contact surface, wherein the integral locking ring includes a flared outer surface, wherein the flared outer surface of the locking ring contacts the flared inner surface of the expandable continuous sealing ring and the expandable gripping ring, wherein the shear landing feature is linked to the integral locking ring.
 7. The method of claim 6, whereby setting the plug assembly includes: expanding the expandable continuous sealing ring and the expandable gripping ring over the flared outer surface of the integral locking ring, whereby the expandable continuous sealing ring and the expandable gripping ring expand radially until the expandable gripping ring contacts and penetrates at least one point of an internal surface of the tubing string.
 8. The method of claim 7, further comprising: applying a pressure, using the well fluid, on the untethered object, on the shear landing feature and on the integral locking ring, whereby resulting forces are applied to the plug assembly to cause: the longitudinal movement of the integral locking ring relative to the expandable gripping ring and to the continuous expandable sealing ring, the radial deformation of the continuous expandable sealing ring over the flared outer surface of the integral locking ring, diverting a portion of the well fluid outside the tubing string, or sealing a portion of the well fluid inside the tubing string with the plug assembly.
 9. The method of claim 1, whereby deploying the plug assembly into the tubing string includes a retrievable toolstring, whereby the retrievable toolstring is retrieved after the setting of the plug assembly into the tubing string, whereby the retrievable toolstring includes an external mandrel and an internal rod.
 10. The method of claim 9, whereby the plug assembly includes: an expandable continuous sealing ring, an expandable gripping ring, a locking ring, a cup, whereby the external mandrel includes a longitudinal stopping surface relative to the locking ring, wherein the expandable continuous sealing ring and the expandable gripping ring include a flared inner surface, wherein the locking ring includes a flared outer surface, a stopping inner surface relative to the cup, a longitudinal stopping surface relative to the external mandrel, and a flared portion, wherein the flared portion of the locking ring includes a flared inner surface positioned opposite of the flared outer surface, wherein the cup includes a flared outer surface, a stopping outer surface and a flared inner surface, wherein the flared outer surface of the locking ring is contacting the flared inner surface of the expandable continuous sealing ring and of the expandable gripping ring, wherein the flared outer surface of the cup is contacting the flared inner surface of the locking ring, wherein the stopping outer surface of the cup is adapted to couple with the stopping inner surface of the locking ring, wherein the longitudinal distance between the stopping outer surface of the cup and the stopping inner surface of the locking ring is a longitudinal gap, wherein the shear landing feature is linked to the integral locking ring.
 11. The method of claim 10, whereby setting the plug assembly includes: expanding the expandable continuous sealing ring and the expandable gripping ring over the flared outer surface of the locking ring, whereby the expandable continuous sealing ring and the expandable gripping ring deforms radially until the expandable gripping ring contacts at least one point of an internal surface of the tubing string, whereby the longitudinal stopping surface of the locking ring relative to the external mandrel and the longitudinal stopping surface of the external mandrel relative to the locking ring are stopped longitudinally relative to each other’s, during the expansion of the expandable continuous sealing ring and of the expandable gripping ring, wherein the longitudinal gap is present between the stopping outer surface of the cup and the stopping inner surface of the locking ring, during the setting of the plug assembly.
 12. The method of claim 11, further comprising: applying pressure on the untethered object, the shear landing feature and on the cup using the well fluid, whereby forces are applied to the plug assembly to cause: the longitudinal movement of the cup relative to the locking ring causing: the closing of the longitudinal gap between the stopping outer surface of the cup and the stopping inner surface of the locking ring, the radial deformation of the flared portion of the locking ring, the radial deformation of the continuous expandable sealing ring, the continuous contact of the continuous expandable sealing ring with the internal surface of the tubing string; and penetrating the internal surface of the tubing string at the at least one point with the expandable gripping ring.
 13. The method of claim 12, further comprising diverting a portion of the well fluid outside the tubing string, or sealing a portion of the well fluid inside the tubing string with the plug assembly.
 14. The method of claim 1, wherein releasing the first-size or the second-size untethered object inside the well fluid of the tubing string includes: launching the untethered object from ground or seabed surface or, freeing the untethered object from the tool string, after the setting of the plug assembly.
 15. A plug assembly, for use inside a tubing string containing well fluid, comprising: a shear landing feature, an expandable continuous sealing ring, an expandable gripping ring, an integral locking ring, a first-size untethered object, wherein the shear landing feature includes a seating surface suited to receive a first-size untethered object, wherein the shear landing feature includes a shear rating, wherein the expandable continuous sealing ring and the expandable gripping ring include a flared inner surface, wherein the first-size untethered object is able to pass through the plug assembly including the fixed seating surface, wherein the integral locking ring includes a flared outer surface and a flared inner surface, wherein the flared outer surface of the locking ring contacts the flared inner surface of the expandable continuous sealing ring and the expandable gripping ring, wherein the retractable pivoting mechanism is linked to the integral locking ring through one or more pivoting axis, whereby the plug assembly includes a fixed seating surface suited to receive a second-size untethered object, wherein the shear landing feature is linked to the integral locking ring.
 16. The apparatus of claim 15, wherein at least one component of the plug assembly comprises a material dissolvable inside the well fluid.
 17. The apparatus of claim 15, wherein the shear landing feature shears in two or more parts, when the force applied on the first-size untethered object exceeds the shear rating of the shear landing feature, wherein the shear rating of the shear landing feature corresponds to a range of 70% to 100% of an overall differential pressure rating of the plug assembly.
 18. The apparatus of claim 15, further including a second-size untethered object, wherein the second-size untethered object is suited to land on the fixed seating surface of the plug assembly. 